#include <iostream>
#include <iomanip>

using namespace std;

int main(){

	double d,e;
	cin >> d;
	if (d <= 20){
		e = d * 1.68;
	}
	else{
		e = d * 1.98;
	}
	cout << fixed << setprecision(2) << e << endl;
    return 0; 
}
